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ip_output.c
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// SPDX-License-Identifier: GPL-2.0-only
/*
* INET An implementation of the TCP/IP protocol suite for the LINUX
* operating system. INET is implemented using the BSD Socket
* interface as the means of communication with the user level.
*
* The Internet Protocol (IP) output module.
*
* Authors: Ross Biro
* Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
* Donald Becker, <becker@super.org>
* Alan Cox, <Alan.Cox@linux.org>
* Richard Underwood
* Stefan Becker, <stefanb@yello.ping.de>
* Jorge Cwik, <jorge@laser.satlink.net>
* Arnt Gulbrandsen, <agulbra@nvg.unit.no>
* Hirokazu Takahashi, <taka@valinux.co.jp>
*
* See ip_input.c for original log
*
* Fixes:
* Alan Cox : Missing nonblock feature in ip_build_xmit.
* Mike Kilburn : htons() missing in ip_build_xmit.
* Bradford Johnson: Fix faulty handling of some frames when
* no route is found.
* Alexander Demenshin: Missing sk/skb free in ip_queue_xmit
* (in case if packet not accepted by
* output firewall rules)
* Mike McLagan : Routing by source
* Alexey Kuznetsov: use new route cache
* Andi Kleen: Fix broken PMTU recovery and remove
* some redundant tests.
* Vitaly E. Lavrov : Transparent proxy revived after year coma.
* Andi Kleen : Replace ip_reply with ip_send_reply.
* Andi Kleen : Split fast and slow ip_build_xmit path
* for decreased register pressure on x86
* and more readability.
* Marc Boucher : When call_out_firewall returns FW_QUEUE,
* silently drop skb instead of failing with -EPERM.
* Detlev Wengorz : Copy protocol for fragments.
* Hirokazu Takahashi: HW checksumming for outgoing UDP
* datagrams.
* Hirokazu Takahashi: sendfile() on UDP works now.
*/
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/highmem.h>
#include <linux/slab.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <net/snmp.h>
#include <net/ip.h>
#include <net/protocol.h>
#include <net/route.h>
#include <net/xfrm.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <net/arp.h>
#include <net/icmp.h>
#include <net/checksum.h>
#include <net/inetpeer.h>
#include <net/inet_ecn.h>
#include <net/lwtunnel.h>
#include <linux/bpf-cgroup.h>
#include <linux/igmp.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter_bridge.h>
#include <linux/netlink.h>
#include <linux/tcp.h>
static int
ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
unsigned int mtu,
int (*output)(struct net *, struct sock *, struct sk_buff *));
/* Generate a checksum for an outgoing IP datagram. */
void ip_send_check(struct iphdr *iph)
{
iph->check = 0;
iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
}
EXPORT_SYMBOL(ip_send_check);
int __ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
{
struct iphdr *iph = ip_hdr(skb);
iph_set_totlen(iph, skb->len);
ip_send_check(iph);
/* if egress device is enslaved to an L3 master device pass the
* skb to its handler for processing
*/
skb = l3mdev_ip_out(sk, skb);
if (unlikely(!skb))
return 0;
skb->protocol = htons(ETH_P_IP);
return nf_hook(NFPROTO_IPV4, NF_INET_LOCAL_OUT,
net, sk, skb, NULL, skb_dst(skb)->dev,
dst_output);
}
int ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
{
int err;
err = __ip_local_out(net, sk, skb);
if (likely(err == 1))
err = dst_output(net, sk, skb);
return err;
}
EXPORT_SYMBOL_GPL(ip_local_out);
static inline int ip_select_ttl(const struct inet_sock *inet,
const struct dst_entry *dst)
{
int ttl = inet->uc_ttl;
if (ttl < 0)
ttl = ip4_dst_hoplimit(dst);
return ttl;
}
/*
* Add an ip header to a skbuff and send it out.
*
*/
int ip_build_and_send_pkt(struct sk_buff *skb, const struct sock *sk,
__be32 saddr, __be32 daddr, struct ip_options_rcu *opt,
u8 tos)
{
const struct inet_sock *inet = inet_sk(sk);
struct rtable *rt = skb_rtable(skb);
struct net *net = sock_net(sk);
struct iphdr *iph;
/* Build the IP header. */
skb_push(skb, sizeof(struct iphdr) + (opt ? opt->opt.optlen : 0));
skb_reset_network_header(skb);
iph = ip_hdr(skb);
iph->version = 4;
iph->ihl = 5;
iph->tos = tos;
iph->ttl = ip_select_ttl(inet, &rt->dst);
iph->daddr = (opt && opt->opt.srr ? opt->opt.faddr : daddr);
iph->saddr = saddr;
iph->protocol = sk->sk_protocol;
/* Do not bother generating IPID for small packets (eg SYNACK) */
if (skb->len <= IPV4_MIN_MTU || ip_dont_fragment(sk, &rt->dst)) {
iph->frag_off = htons(IP_DF);
iph->id = 0;
} else {
iph->frag_off = 0;
/* TCP packets here are SYNACK with fat IPv4/TCP options.
* Avoid using the hashed IP ident generator.
*/
if (sk->sk_protocol == IPPROTO_TCP)
iph->id = (__force __be16)get_random_u16();
else
__ip_select_ident(net, iph, 1);
}
if (opt && opt->opt.optlen) {
iph->ihl += opt->opt.optlen>>2;
ip_options_build(skb, &opt->opt, daddr, rt);
}
skb->priority = sk->sk_priority;
if (!skb->mark)
skb->mark = sk->sk_mark;
/* Send it out. */
return ip_local_out(net, skb->sk, skb);
}
EXPORT_SYMBOL_GPL(ip_build_and_send_pkt);
static int ip_finish_output2(struct net *net, struct sock *sk, struct sk_buff *skb)
{
struct dst_entry *dst = skb_dst(skb);
struct rtable *rt = (struct rtable *)dst;
struct net_device *dev = dst->dev;
unsigned int hh_len = LL_RESERVED_SPACE(dev);
struct neighbour *neigh;
bool is_v6gw = false;
if (rt->rt_type == RTN_MULTICAST) {
IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTMCAST, skb->len);
} else if (rt->rt_type == RTN_BROADCAST)
IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTBCAST, skb->len);
if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
skb = skb_expand_head(skb, hh_len);
if (!skb)
return -ENOMEM;
}
if (lwtunnel_xmit_redirect(dst->lwtstate)) {
int res = lwtunnel_xmit(skb);
if (res < 0 || res == LWTUNNEL_XMIT_DONE)
return res;
}
rcu_read_lock();
neigh = ip_neigh_for_gw(rt, skb, &is_v6gw);
if (!IS_ERR(neigh)) {
int res;
sock_confirm_neigh(skb, neigh);
/* if crossing protocols, can not use the cached header */
res = neigh_output(neigh, skb, is_v6gw);
rcu_read_unlock();
return res;
}
rcu_read_unlock();
net_dbg_ratelimited("%s: No header cache and no neighbour!\n",
__func__);
kfree_skb_reason(skb, SKB_DROP_REASON_NEIGH_CREATEFAIL);
return -EINVAL;
}
static int ip_finish_output_gso(struct net *net, struct sock *sk,
struct sk_buff *skb, unsigned int mtu)
{
struct sk_buff *segs, *nskb;
netdev_features_t features;
int ret = 0;
/* common case: seglen is <= mtu
*/
if (skb_gso_validate_network_len(skb, mtu))
return ip_finish_output2(net, sk, skb);
/* Slowpath - GSO segment length exceeds the egress MTU.
*
* This can happen in several cases:
* - Forwarding of a TCP GRO skb, when DF flag is not set.
* - Forwarding of an skb that arrived on a virtualization interface
* (virtio-net/vhost/tap) with TSO/GSO size set by other network
* stack.
* - Local GSO skb transmitted on an NETIF_F_TSO tunnel stacked over an
* interface with a smaller MTU.
* - Arriving GRO skb (or GSO skb in a virtualized environment) that is
* bridged to a NETIF_F_TSO tunnel stacked over an interface with an
* insufficient MTU.
*/
features = netif_skb_features(skb);
BUILD_BUG_ON(sizeof(*IPCB(skb)) > SKB_GSO_CB_OFFSET);
segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
if (IS_ERR_OR_NULL(segs)) {
kfree_skb(skb);
return -ENOMEM;
}
consume_skb(skb);
skb_list_walk_safe(segs, segs, nskb) {
int err;
skb_mark_not_on_list(segs);
err = ip_fragment(net, sk, segs, mtu, ip_finish_output2);
if (err && ret == 0)
ret = err;
}
return ret;
}
static int __ip_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)
{
unsigned int mtu;
#if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
/* Policy lookup after SNAT yielded a new policy */
if (skb_dst(skb)->xfrm) {
IPCB(skb)->flags |= IPSKB_REROUTED;
return dst_output(net, sk, skb);
}
#endif
mtu = ip_skb_dst_mtu(sk, skb);
if (skb_is_gso(skb))
return ip_finish_output_gso(net, sk, skb, mtu);
if (skb->len > mtu || IPCB(skb)->frag_max_size)
return ip_fragment(net, sk, skb, mtu, ip_finish_output2);
return ip_finish_output2(net, sk, skb);
}
static int ip_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)
{
int ret;
ret = BPF_CGROUP_RUN_PROG_INET_EGRESS(sk, skb);
switch (ret) {
case NET_XMIT_SUCCESS:
return __ip_finish_output(net, sk, skb);
case NET_XMIT_CN:
return __ip_finish_output(net, sk, skb) ? : ret;
default:
kfree_skb_reason(skb, SKB_DROP_REASON_BPF_CGROUP_EGRESS);
return ret;
}
}
static int ip_mc_finish_output(struct net *net, struct sock *sk,
struct sk_buff *skb)
{
struct rtable *new_rt;
bool do_cn = false;
int ret, err;
ret = BPF_CGROUP_RUN_PROG_INET_EGRESS(sk, skb);
switch (ret) {
case NET_XMIT_CN:
do_cn = true;
fallthrough;
case NET_XMIT_SUCCESS:
break;
default:
kfree_skb_reason(skb, SKB_DROP_REASON_BPF_CGROUP_EGRESS);
return ret;
}
/* Reset rt_iif so that inet_iif() will return skb->skb_iif. Setting
* this to non-zero causes ipi_ifindex in in_pktinfo to be overwritten,
* see ipv4_pktinfo_prepare().
*/
new_rt = rt_dst_clone(net->loopback_dev, skb_rtable(skb));
if (new_rt) {
new_rt->rt_iif = 0;
skb_dst_drop(skb);
skb_dst_set(skb, &new_rt->dst);
}
err = dev_loopback_xmit(net, sk, skb);
return (do_cn && err) ? ret : err;
}
int ip_mc_output(struct net *net, struct sock *sk, struct sk_buff *skb)
{
struct rtable *rt = skb_rtable(skb);
struct net_device *dev = rt->dst.dev;
/*
* If the indicated interface is up and running, send the packet.
*/
IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);
skb->dev = dev;
skb->protocol = htons(ETH_P_IP);
/*
* Multicasts are looped back for other local users
*/
if (rt->rt_flags&RTCF_MULTICAST) {
if (sk_mc_loop(sk)
#ifdef CONFIG_IP_MROUTE
/* Small optimization: do not loopback not local frames,
which returned after forwarding; they will be dropped
by ip_mr_input in any case.
Note, that local frames are looped back to be delivered
to local recipients.
This check is duplicated in ip_mr_input at the moment.
*/
&&
((rt->rt_flags & RTCF_LOCAL) ||
!(IPCB(skb)->flags & IPSKB_FORWARDED))
#endif
) {
struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
if (newskb)
NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
net, sk, newskb, NULL, newskb->dev,
ip_mc_finish_output);
}
/* Multicasts with ttl 0 must not go beyond the host */
if (ip_hdr(skb)->ttl == 0) {
kfree_skb(skb);
return 0;
}
}
if (rt->rt_flags&RTCF_BROADCAST) {
struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
if (newskb)
NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
net, sk, newskb, NULL, newskb->dev,
ip_mc_finish_output);
}
return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
net, sk, skb, NULL, skb->dev,
ip_finish_output,
!(IPCB(skb)->flags & IPSKB_REROUTED));
}
int ip_output(struct net *net, struct sock *sk, struct sk_buff *skb)
{
struct net_device *dev = skb_dst(skb)->dev, *indev = skb->dev;
IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);
skb->dev = dev;
skb->protocol = htons(ETH_P_IP);
return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
net, sk, skb, indev, dev,
ip_finish_output,
!(IPCB(skb)->flags & IPSKB_REROUTED));
}
EXPORT_SYMBOL(ip_output);
/*
* copy saddr and daddr, possibly using 64bit load/stores
* Equivalent to :
* iph->saddr = fl4->saddr;
* iph->daddr = fl4->daddr;
*/
static void ip_copy_addrs(struct iphdr *iph, const struct flowi4 *fl4)
{
BUILD_BUG_ON(offsetof(typeof(*fl4), daddr) !=
offsetof(typeof(*fl4), saddr) + sizeof(fl4->saddr));
iph->saddr = fl4->saddr;
iph->daddr = fl4->daddr;
}
/* Note: skb->sk can be different from sk, in case of tunnels */
int __ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl,
__u8 tos)
{
struct inet_sock *inet = inet_sk(sk);
struct net *net = sock_net(sk);
struct ip_options_rcu *inet_opt;
struct flowi4 *fl4;
struct rtable *rt;
struct iphdr *iph;
int res;
/* Skip all of this if the packet is already routed,
* f.e. by something like SCTP.
*/
rcu_read_lock();
inet_opt = rcu_dereference(inet->inet_opt);
fl4 = &fl->u.ip4;
rt = skb_rtable(skb);
if (rt)
goto packet_routed;
/* Make sure we can route this packet. */
rt = (struct rtable *)__sk_dst_check(sk, 0);
if (!rt) {
__be32 daddr;
/* Use correct destination address if we have options. */
daddr = inet->inet_daddr;
if (inet_opt && inet_opt->opt.srr)
daddr = inet_opt->opt.faddr;
/* If this fails, retransmit mechanism of transport layer will
* keep trying until route appears or the connection times
* itself out.
*/
rt = ip_route_output_ports(net, fl4, sk,
daddr, inet->inet_saddr,
inet->inet_dport,
inet->inet_sport,
sk->sk_protocol,
RT_CONN_FLAGS_TOS(sk, tos),
sk->sk_bound_dev_if);
if (IS_ERR(rt))
goto no_route;
sk_setup_caps(sk, &rt->dst);
}
skb_dst_set_noref(skb, &rt->dst);
packet_routed:
if (inet_opt && inet_opt->opt.is_strictroute && rt->rt_uses_gateway)
goto no_route;
/* OK, we know where to send it, allocate and build IP header. */
skb_push(skb, sizeof(struct iphdr) + (inet_opt ? inet_opt->opt.optlen : 0));
skb_reset_network_header(skb);
iph = ip_hdr(skb);
*((__be16 *)iph) = htons((4 << 12) | (5 << 8) | (tos & 0xff));
if (ip_dont_fragment(sk, &rt->dst) && !skb->ignore_df)
iph->frag_off = htons(IP_DF);
else
iph->frag_off = 0;
iph->ttl = ip_select_ttl(inet, &rt->dst);
iph->protocol = sk->sk_protocol;
ip_copy_addrs(iph, fl4);
/* Transport layer set skb->h.foo itself. */
if (inet_opt && inet_opt->opt.optlen) {
iph->ihl += inet_opt->opt.optlen >> 2;
ip_options_build(skb, &inet_opt->opt, inet->inet_daddr, rt);
}
ip_select_ident_segs(net, skb, sk,
skb_shinfo(skb)->gso_segs ?: 1);
/* TODO : should we use skb->sk here instead of sk ? */
skb->priority = sk->sk_priority;
skb->mark = sk->sk_mark;
res = ip_local_out(net, sk, skb);
rcu_read_unlock();
return res;
no_route:
rcu_read_unlock();
IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
kfree_skb_reason(skb, SKB_DROP_REASON_IP_OUTNOROUTES);
return -EHOSTUNREACH;
}
EXPORT_SYMBOL(__ip_queue_xmit);
int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl)
{
return __ip_queue_xmit(sk, skb, fl, inet_sk(sk)->tos);
}
EXPORT_SYMBOL(ip_queue_xmit);
static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
{
to->pkt_type = from->pkt_type;
to->priority = from->priority;
to->protocol = from->protocol;
to->skb_iif = from->skb_iif;
skb_dst_drop(to);
skb_dst_copy(to, from);
to->dev = from->dev;
to->mark = from->mark;
skb_copy_hash(to, from);
#ifdef CONFIG_NET_SCHED
to->tc_index = from->tc_index;
#endif
nf_copy(to, from);
skb_ext_copy(to, from);
#if IS_ENABLED(CONFIG_IP_VS)
to->ipvs_property = from->ipvs_property;
#endif
skb_copy_secmark(to, from);
}
static int ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
unsigned int mtu,
int (*output)(struct net *, struct sock *, struct sk_buff *))
{
struct iphdr *iph = ip_hdr(skb);
if ((iph->frag_off & htons(IP_DF)) == 0)
return ip_do_fragment(net, sk, skb, output);
if (unlikely(!skb->ignore_df ||
(IPCB(skb)->frag_max_size &&
IPCB(skb)->frag_max_size > mtu))) {
IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
htonl(mtu));
kfree_skb(skb);
return -EMSGSIZE;
}
return ip_do_fragment(net, sk, skb, output);
}
void ip_fraglist_init(struct sk_buff *skb, struct iphdr *iph,
unsigned int hlen, struct ip_fraglist_iter *iter)
{
unsigned int first_len = skb_pagelen(skb);
iter->frag = skb_shinfo(skb)->frag_list;
skb_frag_list_init(skb);
iter->offset = 0;
iter->iph = iph;
iter->hlen = hlen;
skb->data_len = first_len - skb_headlen(skb);
skb->len = first_len;
iph->tot_len = htons(first_len);
iph->frag_off = htons(IP_MF);
ip_send_check(iph);
}
EXPORT_SYMBOL(ip_fraglist_init);
void ip_fraglist_prepare(struct sk_buff *skb, struct ip_fraglist_iter *iter)
{
unsigned int hlen = iter->hlen;
struct iphdr *iph = iter->iph;
struct sk_buff *frag;
frag = iter->frag;
frag->ip_summed = CHECKSUM_NONE;
skb_reset_transport_header(frag);
__skb_push(frag, hlen);
skb_reset_network_header(frag);
memcpy(skb_network_header(frag), iph, hlen);
iter->iph = ip_hdr(frag);
iph = iter->iph;
iph->tot_len = htons(frag->len);
ip_copy_metadata(frag, skb);
iter->offset += skb->len - hlen;
iph->frag_off = htons(iter->offset >> 3);
if (frag->next)
iph->frag_off |= htons(IP_MF);
/* Ready, complete checksum */
ip_send_check(iph);
}
EXPORT_SYMBOL(ip_fraglist_prepare);
void ip_frag_init(struct sk_buff *skb, unsigned int hlen,
unsigned int ll_rs, unsigned int mtu, bool DF,
struct ip_frag_state *state)
{
struct iphdr *iph = ip_hdr(skb);
state->DF = DF;
state->hlen = hlen;
state->ll_rs = ll_rs;
state->mtu = mtu;
state->left = skb->len - hlen; /* Space per frame */
state->ptr = hlen; /* Where to start from */
state->offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
state->not_last_frag = iph->frag_off & htons(IP_MF);
}
EXPORT_SYMBOL(ip_frag_init);
static void ip_frag_ipcb(struct sk_buff *from, struct sk_buff *to,
bool first_frag)
{
/* Copy the flags to each fragment. */
IPCB(to)->flags = IPCB(from)->flags;
/* ANK: dirty, but effective trick. Upgrade options only if
* the segment to be fragmented was THE FIRST (otherwise,
* options are already fixed) and make it ONCE
* on the initial skb, so that all the following fragments
* will inherit fixed options.
*/
if (first_frag)
ip_options_fragment(from);
}
struct sk_buff *ip_frag_next(struct sk_buff *skb, struct ip_frag_state *state)
{
unsigned int len = state->left;
struct sk_buff *skb2;
struct iphdr *iph;
/* IF: it doesn't fit, use 'mtu' - the data space left */
if (len > state->mtu)
len = state->mtu;
/* IF: we are not sending up to and including the packet end
then align the next start on an eight byte boundary */
if (len < state->left) {
len &= ~7;
}
/* Allocate buffer */
skb2 = alloc_skb(len + state->hlen + state->ll_rs, GFP_ATOMIC);
if (!skb2)
return ERR_PTR(-ENOMEM);
/*
* Set up data on packet
*/
ip_copy_metadata(skb2, skb);
skb_reserve(skb2, state->ll_rs);
skb_put(skb2, len + state->hlen);
skb_reset_network_header(skb2);
skb2->transport_header = skb2->network_header + state->hlen;
/*
* Charge the memory for the fragment to any owner
* it might possess
*/
if (skb->sk)
skb_set_owner_w(skb2, skb->sk);
/*
* Copy the packet header into the new buffer.
*/
skb_copy_from_linear_data(skb, skb_network_header(skb2), state->hlen);
/*
* Copy a block of the IP datagram.
*/
if (skb_copy_bits(skb, state->ptr, skb_transport_header(skb2), len))
BUG();
state->left -= len;
/*
* Fill in the new header fields.
*/
iph = ip_hdr(skb2);
iph->frag_off = htons((state->offset >> 3));
if (state->DF)
iph->frag_off |= htons(IP_DF);
/*
* Added AC : If we are fragmenting a fragment that's not the
* last fragment then keep MF on each bit
*/
if (state->left > 0 || state->not_last_frag)
iph->frag_off |= htons(IP_MF);
state->ptr += len;
state->offset += len;
iph->tot_len = htons(len + state->hlen);
ip_send_check(iph);
return skb2;
}
EXPORT_SYMBOL(ip_frag_next);
/*
* This IP datagram is too large to be sent in one piece. Break it up into
* smaller pieces (each of size equal to IP header plus
* a block of the data of the original IP data part) that will yet fit in a
* single device frame, and queue such a frame for sending.
*/
int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
int (*output)(struct net *, struct sock *, struct sk_buff *))
{
struct iphdr *iph;
struct sk_buff *skb2;
bool mono_delivery_time = skb->mono_delivery_time;
struct rtable *rt = skb_rtable(skb);
unsigned int mtu, hlen, ll_rs;
struct ip_fraglist_iter iter;
ktime_t tstamp = skb->tstamp;
struct ip_frag_state state;
int err = 0;
/* for offloaded checksums cleanup checksum before fragmentation */
if (skb->ip_summed == CHECKSUM_PARTIAL &&
(err = skb_checksum_help(skb)))
goto fail;
/*
* Point into the IP datagram header.
*/
iph = ip_hdr(skb);
mtu = ip_skb_dst_mtu(sk, skb);
if (IPCB(skb)->frag_max_size && IPCB(skb)->frag_max_size < mtu)
mtu = IPCB(skb)->frag_max_size;
/*
* Setup starting values.
*/
hlen = iph->ihl * 4;
mtu = mtu - hlen; /* Size of data space */
IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
ll_rs = LL_RESERVED_SPACE(rt->dst.dev);
/* When frag_list is given, use it. First, check its validity:
* some transformers could create wrong frag_list or break existing
* one, it is not prohibited. In this case fall back to copying.
*
* LATER: this step can be merged to real generation of fragments,
* we can switch to copy when see the first bad fragment.
*/
if (skb_has_frag_list(skb)) {
struct sk_buff *frag, *frag2;
unsigned int first_len = skb_pagelen(skb);
if (first_len - hlen > mtu ||
((first_len - hlen) & 7) ||
ip_is_fragment(iph) ||
skb_cloned(skb) ||
skb_headroom(skb) < ll_rs)
goto slow_path;
skb_walk_frags(skb, frag) {
/* Correct geometry. */
if (frag->len > mtu ||
((frag->len & 7) && frag->next) ||
skb_headroom(frag) < hlen + ll_rs)
goto slow_path_clean;
/* Partially cloned skb? */
if (skb_shared(frag))
goto slow_path_clean;
BUG_ON(frag->sk);
if (skb->sk) {
frag->sk = skb->sk;
frag->destructor = sock_wfree;
}
skb->truesize -= frag->truesize;
}
/* Everything is OK. Generate! */
ip_fraglist_init(skb, iph, hlen, &iter);
for (;;) {
/* Prepare header of the next frame,
* before previous one went down. */
if (iter.frag) {
bool first_frag = (iter.offset == 0);
IPCB(iter.frag)->flags = IPCB(skb)->flags;
ip_fraglist_prepare(skb, &iter);
if (first_frag && IPCB(skb)->opt.optlen) {
/* ipcb->opt is not populated for frags
* coming from __ip_make_skb(),
* ip_options_fragment() needs optlen
*/
IPCB(iter.frag)->opt.optlen =
IPCB(skb)->opt.optlen;
ip_options_fragment(iter.frag);
ip_send_check(iter.iph);
}
}
skb_set_delivery_time(skb, tstamp, mono_delivery_time);
err = output(net, sk, skb);
if (!err)
IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES);
if (err || !iter.frag)
break;
skb = ip_fraglist_next(&iter);
}
if (err == 0) {
IP_INC_STATS(net, IPSTATS_MIB_FRAGOKS);
return 0;
}
kfree_skb_list(iter.frag);
IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
return err;
slow_path_clean:
skb_walk_frags(skb, frag2) {
if (frag2 == frag)
break;
frag2->sk = NULL;
frag2->destructor = NULL;
skb->truesize += frag2->truesize;
}
}
slow_path:
/*
* Fragment the datagram.
*/
ip_frag_init(skb, hlen, ll_rs, mtu, IPCB(skb)->flags & IPSKB_FRAG_PMTU,
&state);
/*
* Keep copying data until we run out.
*/
while (state.left > 0) {
bool first_frag = (state.offset == 0);
skb2 = ip_frag_next(skb, &state);
if (IS_ERR(skb2)) {
err = PTR_ERR(skb2);
goto fail;
}
ip_frag_ipcb(skb, skb2, first_frag);
/*
* Put this fragment into the sending queue.
*/
skb_set_delivery_time(skb2, tstamp, mono_delivery_time);
err = output(net, sk, skb2);
if (err)
goto fail;
IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES);
}
consume_skb(skb);
IP_INC_STATS(net, IPSTATS_MIB_FRAGOKS);
return err;
fail:
kfree_skb(skb);
IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
return err;
}
EXPORT_SYMBOL(ip_do_fragment);
int
ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
{
struct msghdr *msg = from;
if (skb->ip_summed == CHECKSUM_PARTIAL) {
if (!copy_from_iter_full(to, len, &msg->msg_iter))
return -EFAULT;
} else {
__wsum csum = 0;
if (!csum_and_copy_from_iter_full(to, len, &csum, &msg->msg_iter))
return -EFAULT;
skb->csum = csum_block_add(skb->csum, csum, odd);
}
return 0;
}
EXPORT_SYMBOL(ip_generic_getfrag);
static inline __wsum
csum_page(struct page *page, int offset, int copy)
{
char *kaddr;
__wsum csum;
kaddr = kmap(page);
csum = csum_partial(kaddr + offset, copy, 0);
kunmap(page);
return csum;
}
static int __ip_append_data(struct sock *sk,
struct flowi4 *fl4,
struct sk_buff_head *queue,
struct inet_cork *cork,
struct page_frag *pfrag,
int getfrag(void *from, char *to, int offset,
int len, int odd, struct sk_buff *skb),
void *from, int length, int transhdrlen,
unsigned int flags)
{
struct inet_sock *inet = inet_sk(sk);
struct ubuf_info *uarg = NULL;
struct sk_buff *skb;
struct ip_options *opt = cork->opt;
int hh_len;
int exthdrlen;
int mtu;
int copy;
int err;
int offset = 0;
bool zc = false;
unsigned int maxfraglen, fragheaderlen, maxnonfragsize;
int csummode = CHECKSUM_NONE;
struct rtable *rt = (struct rtable *)cork->dst;
unsigned int wmem_alloc_delta = 0;
bool paged, extra_uref = false;
u32 tskey = 0;
skb = skb_peek_tail(queue);
exthdrlen = !skb ? rt->dst.header_len : 0;
mtu = cork->gso_size ? IP_MAX_MTU : cork->fragsize;
paged = !!cork->gso_size;
if (cork->tx_flags & SKBTX_ANY_TSTAMP &&
sk->sk_tsflags & SOF_TIMESTAMPING_OPT_ID)
tskey = atomic_inc_return(&sk->sk_tskey) - 1;
hh_len = LL_RESERVED_SPACE(rt->dst.dev);
fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);